We study the potential of reflectance photoplethysmography (PPG) in monitoring free flaps for arterial and venous thrombosis in post-surgical scenarios. Circulatory disruptions due to thrombosis were simulated using limb ischemia method on 30 volunteers. Arterial and venous occlusions were conducted in this study. The variation in blood flow in the region of interest was captured by a custom built sensor and data acquisition system using dual wavelength reflectance photoplethysmography. The main chromophores in blood, oxygenated and reduced hemoglobin, showed good variation to visible - near infrared wavelengths with concentration and volume changes. Sensitivity of the prototype device in detecting arterial and venous circulation disruptions was evaluated at various different threshold levels of signal parameters. The device showed strong capability to accurately detect circulatory disruptions and has potential in post-surgical monitoring of free flaps. © 2016 IEEE.